The present disclosure relates to, among recording devices, such as fax machines, copiers, printers, etc., inkjet recording devices which perform recording by ejecting ink to a recording medium, such as paper, and image forming apparatuses.
Recording devices, such as fax machines, copiers, printers, etc., which record an image to a recording medium, such as paper, cloth, transparency films, etc., include an inkjet type, a wire dot type, a thermal type, etc. according to recording methods. Further, the inkjet recording type includes serial printing and line head printing, for example. In the inkjet recording of serial printing type, recording is performed while recording heads perform scan on the recording medium, for example. In the inkjet recording of line head type, recording is performed by single path type (one path type), for example. In inkjet recording devices employing the inkjet recording of line head type, the recording heads in lines are fixed to a device body, for example.
Referring to such an inkjet recording device, since no caps is fitted on their nozzle surfaces, moisture in the ink may evaporate from ejection nozzles in a non-ejecting state, such as ejection nozzles under a wait condition or between sheets of paper in consecutive printing and ejection nozzles that are not used in printing. This increases the viscosity of the ink. As a result, printed patterns may be disarranged, and ejection failure may be caused thereafter.
In particular, in the recording scheme of the line head type, in which the recording heads are fixed, since respective nozzles of the recording heads correspond to respective specified pixels (dots) in one line of an image, nozzles (e.g., nozzles corresponding to pixels in right and left margins, etc.) may be present which do not perform ink ejection at all in printing a whole image. Even such the nozzles may perform dot formation thereafter in another image data. The nozzles in this case are required to perform stable ink ejection.
In general, in order to prevent ink drying and nozzle clogging in the ejection nozzles with openings formed in the ink ejection surfaces of the recording heads, after the ink is forcedly ejected from the nozzles, the ink adhering to the ink ejection surfaces is wiped off for recovery of the recording heads. However, this process may increase wasted ink not used in printing. Further, not only nozzles that do not perform ink ejection but also nozzles immediately after ink ejection are subjected to forced ink ejection, which is inefficient.
Incidentally, piezoelectric inkjet heads are widely used as the recording heads for the inkjet recording devices. In general, a piezoelectric element of a piezoelectric inkjet head deforms to change the volume of the inside of a pressurizing chamber for oscillation of an ink meniscus in a nozzle, thereby generating an ink droplet.
Thereupon, a method for preventing nozzle clogging by oscillating an ink meniscus in a nozzle to the extent that the ink is not ejected from the nozzle has been proposed. For example, in some inkjet printer, it is examined to oscillate the ink meniscus using a plurality of consecutive pulses at a frequency higher than a drive waveform so that a droplet is ejected.
Referring further to another method of driving a droplet ejecting head, a piezoelectric element is driven by a drive waveform generated using stand-by drive power in a non-printing state when no image data is input, thereby oscillating the meniscus of a nozzle of the ejection head.
Furthermore, the following is also examined. That is, drive voltage of a piezoelectric element is discharged in a dot formation section, which does not eject an ink droplet, to increase the volume of the pressurizing chamber, thereby bringing the ink meniscus in a nozzle toward a pressurizing chamber. Then, the drive voltage is applied again at timing almost in coincidence with the natural oscillation period of the volume velocity of the ink to reduce the volume of the pressurizing chamber. Thus, the ink meniscus is oscillated without ejecting the ink droplet from the nozzle to stir the ink in the nozzle.
It is also examined that an identical nozzle in an image forming apparatus is subjected to meniscus oscillation for at least one pixel except a pixel immediately before a to-be-plotted pixel out of pixels that are not consecutively plotted predetermined times that is larger than 1, but is not subjected to meniscus oscillation for a pixel immediately before the to-be-plotted pixel. Further examined is the use of a drive pulse close to the natural oscillation period of head paths as a drive pulse for meniscus oscillation.